98557046 Summer Training Report At B H E L Bhopal 705q2y

VOCATIONAL TRAINING REPORT, DEC-2015 PROJECT INCHARGE: .

SUBMITTED BY: PANKAJ MODI 3rd YEAR STUDENT DEPT. OF ELECTRICAL ENGINEERING MAULANA AZAD NATIONAL INSTITUTE OF TECHNOLOGY BHOPAL (M.P.)

TRAINING DURATION: 1

03 DEC. 2015 TO 30 DEC. 2015

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ACKNOWLEDGEMENTS I would sincerely like to express my gratitude for BHEL Bhopal, for providing me the opportunity of pursuing my vocational training in this renowned industry and endowing me with an unparallel experience and deep understanding of a wide array of processes and manufacturing methods taking place in different workshops of the industry. I would also take this opportunity to thank our training in-charge, Mr. A.K. Dhimaan whose guidance and motivation went a long way in our understanding of different sections of the industry. Furthermore, I would thank my institute, MANIT Bhopal, for giving me opportunity of visiting this industry and increasing my practical knowledge. Last, but not the least, I would also like to acknowledge the immense pleasure, brought about by my friends as they pursued their training along with me. We shared some unforgettable moments together. 3

Thank you all. PANKAJ MODI BHEL OVERVIEW BHEL was established more than 50 years ago when its first plant was setup in Bhopal ushering in the indigenous Heavy Electrical Equipment Industry in India. BHEL is largest engineering and manufacturing enterprise in India in the energy related/infrastructure sector. BHEL was established more than four decades ago ushering in the indigenous Heavy Electrical Equipment industry in India. BHEL has built over the years, a robust domestic market position by becoming the largest supplier of power plant equipment in India, and by developing strong market presence in select segment of the industry sector and the Railway. Currently, 80% of the Nuclear power generation in the country is through BHEL sets. A dream which has been more than realized with a well recognized track record of performance it has been earning profits continuously since 1971-72 and achieved a turnover of Rs 2,658 crore for the year 2007-08, showing a growth of 17 per cent . Bharat Heavy Electricals Limited is country’s ‘Navratna’ company and has earned its place among very prestigious national and international companies. It finds place among the top class companies of the world for manufacture of electrical equipments. 4

BHEL caters to core sectors of the Indian Economy viz., Power Generation's & Transmission, Industry, Transportation, Telecommunication, Renewable Energy, Defense, etc. BHEL has already attained ISO 9000 certification for quality management, and ISO 14001 certification for environment management and OHSAS – 18001 certification for Occupational Health and Safety Management Systems. The Company today enjoys national and international presence featuring in the “Fortune International -500” and is ranked among the top 10 companies in the world, manufacturing power generation equipment. BHEL is the only PSU among the 12 Indian companies to figure in “Forbes Asia Fabulous 50” list. Probably the most significant aspect of BHEL’s growth has been its diversification .The constant reorientation of the organization to meet the varied needs in time with a philosophy that has led to total development of a total capability from concepts to commissioning not only in the field of energy but also in industry and transportation. In the world power scene BHEL ranks among the top ten manufacturers of power plant equipments not only in spectrum of products and services offered, it is right on top. BHEL‘s technological excellence and turnkey capabilities have won it worldwide recognition. Over 40 countries in world over have placed orders with BHEL covering individual equipment to complete power stations on turnkey basis BHEL has 5

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Installed equipment for over 90000MW of power generation-for utilities, captive and industrial s. Supplied over 225000MW a transformer capacity and other equipment operating in transmission and distribution network up to 400Kv (AC& DC). Supplied over 25000 motors with drive control system to power projects, petro chemicals, refineries, steel, aluminum, fertilizers, cement plants etc. Supplied traction electrics and AC/DC locos to power over 12000kms railway network. Supplied over one million valves to power plants and other industries.

BHEL manufactures over 180 products under 30 major product groups and caters to core sectors of the Indian Economy viz., Power Generation & Transmission, Industry, Transportation, Telecommunication, Renewable Energy, etc. The wide network of BHEL's 14 manufacturing divisions, four Power Sector regional centers, over 100 project sites, eight service centers and 18 regional offices, enables the Company to promptly serve its customers and provide them with suitable products, systems and services -- efficiently and at competitive prices. The high level of quality & reliability of its products is due to the emphasis on design, engineering and manufacturing to international standards by acquiring and adapting some of the best technologies from leading companies in the world, together with technologies developed in its own R&D centers. 

BHEL has acquired certifications to Quality Management Systems (ISO 9001), Environmental 6

Management Systems (ISO 14001) and Occupational Health & Safety Management Systems (OHSAS 18001) and is also well on its journey towards Total Quality Management. 

BHEL vision is to become a world class engineering enterprise, committed to enhancing stakeholder value. The company is striving to give shape to its aspiration and fulfill the expectations of the country to become a global presence:-

Vision: “A world class engineering enterprise committed to enhance stakeholder values.” Mission: “To be an Indian multinational engineering providing total business solution through quality product system and services in the field of energy, transportation, industry, infrastructure and other potential area. Values: 

Ensure speed of response.

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Foster learning, creativity and team work.

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Respect for dignity and potential of individuals

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Loyalty and pride in company 7

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Zeal for the change.

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Zeal to excel.

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Integrity and fairness in all matters.

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Strict adherence to commitments.

BUSINESS MISSION To maintain a leading position as supplier of quality equipments, system and services in the field of conversion, transmission, utilization, and conversation of energy for application in the area of electric power, transportation oil and gas exploration and industries. To utilize company’s capability and resources to expand busyness in to allied area an priority sector of economy like defense, communication and electronics. BHEL OBJECTIVES A dynamic organization is one which keeps its aim high, adopts itself quickly to changing environment, so we are in BHEL. The objectives of the company have been redefined in the corporate plane for 90’s. Growth To ensure a steady growth by enhancing the competitive edge of BHEL in existing busyness, new area and international market so as to fulfill national expectation from BHEL. 8

Profitability To ensure a reasonable and adequate return on capital employed, primarily through improvements in operation, efficiency, capacity utilization & productivity and to generate adequate internal resources to finance the company’s growth. Focus To built a high degree of customer confidence by providing increased value of his money through international standards of product quality performance and superior customer service. People Orientation To enable each employee to achieve his potential, improve his capabilities, understand is role and responsibilities and participate and contribute to the growth and success of the company. Technology To achieve technological excellence in operation of indigenous technologies and efficient absorption and adoption of imparted technologies to suit business. Image To fulfill the expectations, which stack holders like government as owner employee, customer and the country at large have from BHEL. 9

BHEL BHOPAL PROFILE

Heavy Electrical Plant, Bhopal is the mother plant of Bharat Heavy Electricals Limited, the largest engineering and manufacturing enterprise inIndia in the energy-related and infrastructure sector, today. It is located at about 7 kms. from Bhopal Railway station, about 5 kms. from Habibganj Railway station and about 18 kms. From Raja Bhoj Airport. With technical assistance from Associated Electricals (India) Ltd., a UK based company, it came into existence on 29th of August, 1956. Pt. Jawaharlal Nehru, first Prime minister of India dedicated this plant to the nation on 6th of November, 1960. BHEL, Bhopal with state-of-the-art facilities, manufactures wide range of electrical equipments. Its product range includes Hydro, Steam, Marine & Nuclear Turbines, Heat Exchangers, Hydro & Turbo Generators, Transformers, Switchgears, Control gears, Transportation Equipment, Capacitors, Bushings, Electrical Motors, Rectifiers, Oil Drilling Rig Equipments and Diesel Generating sets. 10

BHEL, Bhopal certified to ISO: 9001, ISO 14001 and OHSAS 18001, is moving towards excellence by adopting TQM as per EFQM / CII model of Business Excellence. Heat Exchanger Division is accredited with ASME ‘U’ Stamp. With the slogan of “Kadam kadam milana hai, grahak safal banana hai”, it is committed to the customers. BHEL Bhopal has its own Laboratories for material testing and instrument calibration which are accredited with ISO 17025 by NABL. The Hydro Laboratory, Ultra High Voltage laboratory and Centre for Electric Transportation are the only laboratories of its in this part of theworld. BHEL Bhopal's strength is it's employees. The company continuously invests in Human Resources and pays utmost attention to their needs. The plant's Township, well known for its greenery is spread over an area of around 20 sq kms. and provides all facilities to the residents like, parks, community halls, library, shopping centers, banks, post offices etc. Besides, free health services is extended to all the employees through 350 bedded (inclusive of 50 floating beds) Kasturba Hospital and chain of dispensaries. BHEL – BUSINESS AREAS BHEL today is the largest Engineering Enterprise of its kind in India with excellent track record of performance, making profits continuously since 1971-72. 11

BHEL's operations are organised around three business sectors, namely Power, Industry - including Transmission, Transportation, Telecommunication & Renewable Energy - and Overseas Business. This enables BHEL to have a strong customer orientation, to be sensitive to his needs and respond quickly to the changes in the market. 

Power

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Industry

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Transportation

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Transmission

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Defenses etc.

The greatest strength of BHEL is its highly skilled and committed 42,600 employees. Every employee is given an equal opportunity to develop himself and grow in his career. Continuous training and retraining, career planning, a positive work culture and participative style of management all these have engendered development of a committed and motivated workforce setting new benchmarks in of productivity, quality and responsiveness. POWER SECTOR Power is the core sector of BHEL and comprises of thermal, nuclear gas, diesel and hydro business. Today BHEL 12

supplied sets, s for nearly 66 % of the total installed capacity in the country as against nil till 1969-70. BHEL manufactures boilers auxiliaries, TG sets and associate controls, piping and station C & I up to 500 MW rating with technology and capability to go up to 1000 MW range. The auxiliary products high value capital equipment like bowl and tube mills, pumps and heaters, electrostatic precipitators, gravimetric feeders, fans, valves etc. BHEL has contracted so far around 240 thermal sets of various ratings, which includes 14 power plants set up on turnkey basis. Nearly 85 % of World Bank tenders for thermal sets floated in India have been won by the company against international competition. BHEL has adopted the technology to the needs of the country and local conditions. This has led to the development of several technologies in house. The fluidized bed boiler that uses low graded high-ash abrasive Indian coal is an outcome of such an effort. With large-scale availability of natural gas and the sudden increase in demand, BHEL began to manufacture gas turbines and now possesses two streams of gas turbine technology. It has the capability to manufacture gas turbines up to 200 MW rating and custom built combined cycle power plants. Nuclear steams generators, turbine generators, sets and related equipment of 235 MW rating have been supplied to most of the nuclear power plants in India. Production of 500 MW nuclear sets, for which orders have been received. BHEL has developed expertise in renovation and maintenance of power plant equipment besides specialized 13

know how of residual life assessment, health diagnostic and life extensions of plants. The four power sectors regional centers at New Delhi, Chennai, Kolkata and Nagpur will play a major role in giving a thrust to this business and focus BHEL's efforts in this area. As part of India’s largest Solar Power-based Island Electrification Project in India, Bharat Heavy Electricals Limited (BHEL) has successfully commissioned two GridInteractive Solar Power Plants of 100 KW each in Lakshadweep. With this, the company has commissioned a total of eleven Solar Power Plants in the Lakshadweep islands, adding over 1 MW of Solar Power to the power generating capacity of the coral islands in the Arabian Sea.  BHEL has proven turnkey capabilities for executing power projects from concept to commissioning and manufactures boilers, thermal turbine generator sets and auxiliaries up to 500MW.  It possesses the technology and capability to procure thermal power generation up to 1000MW.  Co- generation and combined cycle plants have also been introduced.  For the efficient use of high ash content coal BHEL supplies circulating fluidized boiler.  BHEL manufacturers 235MW nuclear sets and has also commenced production of 500MW nuclear turbine generator sets. Custom made hydro sets of Francis, pelton and kepian types for different head discharge combination are also engineering and manufactured by BHEL. 14

In, all 700 utility sets of thermal, hydro, gas and nuclear have been placed on the company as on date. The power plant equipment manufactured by BHEL is based on contemporary technology comparable to the best in the world and is also internationally competitive. The Company has proven expertise in Plant Performance Improvement through renovation modernization and up rating of variety of power plant equipment besides specialized know how of residual life assessment, health diagnostics and life extension of plants. POWER TRANSMISSION AND DISTRIBUTION (T&D)

BHEL offer wide-ranging products and systems for T & D applications Products. manufactured include power transformers, instrument transformers, dry type transformers, series – and shunt reactor, capacitor tanks, vacuum – and SF circuit breakers gas insulated switch gears and insulators. A strong engineering base enables the Company to undertake turnkey delivery of electric substances up to 400 kV level series compensation systems (for increasing power transfer capacity of transmission lines and improving system stability and voltage regulation), shunt compensation systems (for power factor and voltage improvement) and HVDC systems (for economic transfer of bulk power). BHEL has indigenously developed the state-of-the-art controlled shunt reactor (for reactive power management on long transmission 15

lines). Presently a 400 kV Facts (Flexible AC Transmission System) project under execution. A wide range of transmission products and systems are produced by BHEL to meet the needs of power transmission and distribution sector. These include:     

Dry Type Transformers SF6 Switch Gears 400 KW Transmission Equipment High Voltage Direct Current System Series and Shunt Compensation Systems

In anticipation of the need for improved substations, a 33 KV gas insulated substation with micro processors base control and protection system has been done. INDUSTRY SECTOR BHEL is a major contributor of equipment and system to important industries like      

Cement Petrochemicals Fertilizers Steel papers Refineries Mining and telecommunication

BHEL has indigenously developed the state-of-the-art controlled shunt reactor (for reactive power management on long transmission lines). Presently a 400 kV FACTS (Flexible AC Transmission System) projects is under execution. 16

The range of system and equipment supplied includes:      

Captive power plants High speed industrial drive turbines Industrial boilers and auxiliaries Waste heat recovery boilers Gas turbine pump, valves, seamless steel tubes Heat exchangers Process control etc.

The Company is a major producer of large-size thruster devices. It also supplies digital distributed control systems for process industries, and control & instrumentation systems for power plant and industrial applications. BHEL is the only company in India with the capability to make simulators for power plants, defense and other applications. The Company has commenced manufacture of large desalination plants to help augment the supply of drinking water to people. TRANSPORTATION BHEL is involved in the development design, engineering, marketing, production, installation, and maintenance and after-sales service of Rolling Stock and traction propulsion systems. In the area of rolling stock, BHEL manufactures electric locomotives up to 5000 HP, dieselelectric locomotives from 350 HP to 3100 HP, both for mainline and shunting duly applications. BHEL is also producing rolling stock for special applications viz., overhead equipment cars, Special well wagons, Rail-cum-road vehicle 17

etc., Besides traction propulsion systems for in-house use, BHEL manufactures traction propulsion systems for other rolling stock producers of electric locomotives, diesel-electric locomotives, electrical multiple units and metro cars. The electric and diesel traction equipment on India Railways are largely powered by electrical propulsion systems produced by BHEL. The company also undertakes retooling and overhauling of rolling stock in the area of urban transportation systems. BHEL is geared up to turnkey execution of electric trolley bus systems, light rail systems etc. BHEL is also diversifying in the area of port handing equipment and pipelines transportation systems. 

65 % of trains in Indian Railways are equipped with BHEL's traction and traction control equipment. These include:  Broad Gauge 3900 HP AC / DC locomotives  Diesel Shunting Locomotives up to 2600 HP  5000 HP AC Loco with thyristor control  Battery Powered Road Vehicles and Locomotives

TELECOMMUNICATION BHEL also caters to telecommunication sector by way of small, medium and large switching system. Renewable energy Technologies that can be offered by BHEL for exploiting non-conventional and renewable resources of energy includes: wind electric generators, solar power based water pumps, lighting and heating systems. 18

The company manufactures wind electric generators of unit size up to 250 KW for wind farms, to meet the growing demand for harnessing wind energy. International operations BHEL has, over the years established its references in over 50 countries of the world, ranging from the united-states in the west to new-Zealand in the far-east. These references encom almost the entire product range of BHEL, covering turnkey power projects of thermal, hydro and gas based type sub-station projects, rehabilitation projects, besides a wide variety of products, like switch gear, transformer, heat exchangers, insulators, castings and forgings. Apart from over 1100MW of boiler capacity contributed in Malaysia, some of the other major successes achieved by the company have been in Oman, Saudi Arabia, Libya, Greece, Cyprus, Malta, Egypt, Bangladesh, Azerbaijan, Sri lanka, Iraq etc. execution of overseas projects has also provided BHEL the experience of working with world renowned consulting organizations and inspection agencies. RESEARCH AND DEVELOPMENT(R&D) To remain competitive and meet customers’ expectations, BHEL lays great emphasis on the continuous up gradation of products and related technologies, and development of new products. The company has upgraded its products to contemporary levels through continuous in house efforts as well as through acquisitions of new technologies from leading engineering organizations of the world.

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Research and product development centers at each of the manufacturing divisions play a complementary role. BHEL’s investment in R&D is amongst the largest in the corporate sector in India. BHEL's vision is to become a world-class engineering enterprise, committed to enhancing stakeholder value. The company is striving to give shape to its aspirations and fulfill the expectations of the country to become a global player. The greatest strength of BHEL is its highly skilled and committed 42,600 employees. Every employee is given an equal opportunity to develop himself and grow in his career. Continuous training and retraining, career planning, a positive work culture and participative style of management – all these have engendered development of a committed and motivated workforce setting new benchmarks in of productivity, quality and responsiveness. BHEL has a corporate R & D center ed by R & D groups at each of the manufacturing divisions. The dedicated effort of BHEL's R & D engineers have produced several new products like automated storage retrieval system automated guide vehicles for material transportation etc. Establishment of Asia's largest fuel evaluation test facility at Tiruchi was high light of the year. This facility will enable evaluation of combustion, heat transfer and pollution parameters in boilers. Major R & D achievement include:

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Design manufacture and supply of countries first 17.2 MW industrial steam turbines. Development of 4700 HP AC / DC loco for Indian Railways. Development of largest capacitor voltage transformers of 8800 PF 400 KV rating. Development and application low cost ROBOTS for job loading/unloading.

According to ex- CMD Mr. R.K.D. Shah, "BHEL is spending Rs. 60 Crores on Research and Development. Earning from product which has been commercialized has gone up 26 % to Rs. 760 Crores." PRODUCTS Thermal Power Plants  Steam turbines, boilers and generators of up to 800 MW capacity for utility and combined-cycle applications ; Capacity to manufacture boilers and steam turbines with supercritical system cycle parameter and matching generator up to 1000 MW unit size. 

Steam turbines, boilers and generators of P applications; capacity to manufacture condensing, extraction, back pressure, injection or any combination of these types of steam turbines.

Nuclear Power Plants  Steam generator & Turbine generator up to 700 MW capacity. Gas-Based Power Plants 21

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Gas turbines of up to 280 MW (ISO) advance class rating. Gas turbine-based co-generation and combined-cycle systems of industry and utility applications.

There are other products given as follows Hydro Power Plants, DG Power Plants, Industrial Sets, Boiler, Boiler Auxiliaries, Piping System, Heat Exchangers and Pressure Vessels Pumps, Power Station Control Equipment, Switchgear, Bus Ducts, Transformers, Insulators, Industrial and Special Ceramics, Capacitors, Electrical Machines, Compressors, Control Gear, Silicon Rectifiers, Thyristor GTO/IGBT Equipment , Power Devices, Transportation Equipment Oil Field Equipment, Casting and Forgings, Seamless Steel Tubes, Distributed Power Generation and Small Hydro Plants. TECHNICAL COLLABORATIONS PRODUCT COLLABORATIONS # Thermal Sets, Hydro Sets, Motors & Control Gears. # By & Pressure Reducing Systems Ltd.

Prommashexport RUSSIA Sulzer Brother

SWITZERLAND # Electronic Automation System for

Siemens AG. 22

Steam Turbine & Generators



# Francis Type Hydro Turbines

General Electric CANADA

# Moisture Separator Reheaters # Christmas Trees & Conventional Well Well

Baloke Duerr National Oil Head

Assemblies, USA # Steam Turbines , Generators and Axial Condensers # Cam Shaft Controllers and Tractions Current Control Units

Siemens AG. Siemens AG.

MAJOR CUSTOMERS OF B.H.E.L 

Supplied to all major utilities in India : National Thermal Power Corporation (NTPC) PGCIL NJPC NHPC NLC NPCIL NEEPCO APTRANSCO APGENCO JPPCL ALL State Electricity Boards (SEBs) 23

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Abroad: TNB,Malaysia PPC,Greece MEW,Oman OCC,Oman GECOL,Libya Trinidad & Tobago New Zealand Tanzania etc

MAJOR COMPETITORS OF BHEL Ansaldo 2. Asea Brown Boueri 3. Beehtel 4. Block & Neatch 5. CNMI & EC 6. Costain 7. Electrim 8. Energostio 9. Electro Consult 10. Franco Tosi 11. Fuji 12. GEC Alsthom 13. General Electric 14. Hitachi 15. LMZ 16. Mitsubishi 17. Mitsui 18. NEI 19. Raytheon 1.

Italy Switzerland USA USA China U.K. Poland Russia Italy Japan U.K. USA Japan Russia Japan Japan U.K. USA 24

20. 21.

Rolls Royce Sanghai Electric Co.

China

DIVISIONS OF BHEL There are 20 Divisions of BHEL, they are as follows:                    

HEEP, Haridwar HPEP, Hyderabad HPBP, Tiruchi SSTP & MHD, Tiruchi CFFP, Haridwar BHEL, Jhansi BHEL, Bhopal EPD, Bangalore ISG, Bangalore ED, Bangalore BAP, Ranipet IP, Jagdishpur IOD, New Delhi COTT, Hyderabad IS, New Delhi CFP, Rudrapur HERP, Varanasi Regional Operations Division ARP, New Delhi TPG, Bhopal Power Group (Four Regions and PEM)

MANUFACTURING UNIT OF BHEL First Generation Units BHOPAL

Heavy Electrical Plant 25

HARIDWAR

Heavy Electrical Equipment Plant

HYDERABAD

Heavy Electrical Power Equipment

TIRUCHY

High Pressure Boiler Plant

Plant

Second Generation Units JHANSI

Transformer and Locomotive Plant

HARDWAR

Central Foundry and Forge Plant

TIRUCHY

Seamless Steel Tube Plant

Unit Through Acquisition and Merger BANGALORE Electronic Division Electro Porcelain Division New Manufacturing Units RANIPAT

Boiler Auxiliaries Plant

JAGDISHPUR

Insulator Plant

RUDRAPUR

Component and Fabrication Plant

BANGALORE

Industrial System Group TRANSFORMERS 26

A transformer is a device that transfers electrical energyfrom one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF), or "voltage", in the secondary winding. This effect is called inductive coupling. If a load is connected to the secondary, current will flow in the secondary winding, and electrical energy will be transferred from the primary circuit through the transformer to the load. In an ideal transformer, the induced voltage in the secondary winding (Vs) is in proportion to the primary voltage (Vp) and is given by the ratio of the number of turns in the secondary (Ns) to the number of turns in the primary (Np) as follows:

By appropriate selection of the ratio of turns, a transformer thus enables an alternating current (AC) voltage to be "stepped up" by making Ns greater than Np, or "stepped down" by making Ns less than Np. The windings are coils wound around a ferromagnetic core, air-core transformers being a notable exception. Transformers range in size from a thumbnail-sized coupling transformer hidden inside a stage microphone to huge units weighing hundreds of tons used to interconnect portions ofpower grids. All operate on the same basic principles, although the range of designs is wide. While new technologies have eliminated the need for transformers in some electronic 27

circuits, transformers are still found in nearly all electronic devices designed for household ("mains") voltage. Transformers are essential for high-voltage electric power transmission, which makes long-distance transmission economically practical. BASIC PRINCIPLES

An ideal transformer. The secondary current arises from the action of the secondary EMF on the (not shown) load impedance. The transformer is based on two principles: first, that an electric current can produce a magnetic field(electromagnetism) and second that a changing magnetic field within a coil of wire induces a voltage across the ends of the coil (electromagnetic induction). Changing the current in the primary coil changes the magnetic flux that is developed. The changing magnetic flux induces a voltage in the secondary coil. An ideal transformer is shown in the adjacent figure. Current ing through the primary coil creates amagnetic field. The primary and secondary coils are wrapped around 28

a core of very high magnetic permeability, such as iron, so that most of the magnetic flux es through both the primary and secondary coils. If a load is connected to the secondary winding, the load current and voltage will be in the directions indicated, given the primary current and voltage in the directions indicated (each will be alternating current in practice). Induction law The voltage induced across the secondary coil may be calculated from Faraday's law of induction, which states that:

where Vs is the instantaneous voltage, Ns is the number of turns in the secondary coil and Φ is the magnetic flux through one turn of the coil. If the turns of the coil are oriented perpendicularly to the magnetic field lines, the flux is the product of the magnetic flux density B and the area A through which it cuts. The area is constant, being equal to the crosssectional area of the transformer core, whereas the magnetic field varies with time according to the excitation of the primary. Since the same magnetic flux es through both the primary and secondary coils in an ideal transformer, the instantaneous voltage across the primary winding equals

Taking the ratio of the two equations for Vs and Vp gives the basic equation for stepping up or stepping down the voltage

Np/Ns is known as the turns ratio, and is the primary functional characteristic of any transformer. In the case of step29

up transformers, this may sometimes be stated as the reciprocal, Ns/Np. Turns ratio is commonly expressed as an irreducible fraction or ratio: for example, a transformer with primary and secondary windings of, respectively, 100 and 150 turns is said to have a turns ratio of 2:3 rather than 0.667 or 100:150.

Ideal power equation

The ideal transformer as a circuit element If the secondary coil is attached to a load that allows current to flow, electrical power is transmitted from the primary circuit to the secondary circuit. Ideally, the transformer is perfectly efficient. All the incoming energy is transformed from the primary circuit to the magnetic field and into the secondary circuit. If this condition is met, the input electric power must equal the output power: giving the ideal transformer equation

This formula is a reasonable approximation for most commercial built transformers today. 30

If the voltage is increased, then the current is decreased by the same factor. The impedance in one circuit is transformed by the square of the turns ratio.For example, if an impedance Zs is attached across the terminals of the secondary coil, it appears to the primary circuit to have an impedance of (Np/Ns)2Zs. This relationship is reciprocal, so that the impedance Zp of the primary circuit appears to the secondary to be (Ns/Np)2Zp. Detailed operation The simplified description above neglects several practical factors, in particular, the primary current required to establish a magnetic field in the core, and the contribution to the field due to current in the secondary circuit. Models of an ideal transformer typically assume a core of negligible reluctance with two windings of zero resistance. When a voltage is applied to the primary winding, a small current flows, driving flux around the magnetic circuit of the core.: The current required to create the flux is termed the magnetizing current. Since the ideal core has been assumed to have near-zero reluctance, the magnetizing current is negligible, although still required, to create the magnetic field. The changing magnetic field induces an electromotive force (EMF) across each winding. Since the ideal windings have no impedance, they have no associated voltage drop, and so the voltages VP and VSmeasured at the terminals of the transformer, are equal to the corresponding EMFs. The primary EMF, acting as it does in opposition to the primary voltage, is sometimes termed the "back EMF". This is in accordance with Lenz's law, which states that induction of EMF always opposes development of any such change in magnetic field. 31

Core form and shell form transformers

Core form = core type; shell form = shell type As first mentioned in regard to earliest ZBD closed-core transformers, transformers are generally considered to be either core form or shell form in design depending on the type of magnetic circuit used in winding construction (see image). That is, when winding coils are wound around the core, transformers are termed as being of core form design; when winding coils are surrounded by the core, transformers are termed as being of shell form design. Shell form design may be more prevalent than core form design for distribution transformer applications due to the relative ease in stacking the core around winding coils Core form design tends to, as a general rule, be more economical, and therefore more prevalent, than shell form design for high voltage power transformer applications at the lower end of their voltage and power rating ranges (less than or equal to, nominally, 230 kV or 75 MVA). At higher voltage and power ratings, shell form transformers tend to be more prevalent. Shell form design tends to be preferred for extra high voltage and higher MVA applications because, though more labor intensive to manufacture, shell form transformers are 32

characterized as having inherently better kVA-to-weight ratio, better short-circuit strength characteristics and higher immunity to transit damage.

EQUIVALENT CIRCUIT

Transformer equivalent circuit, impedances referred to the primary side

with

secondary

The parameters of equivalent circuit of a transformer can be calculated from the results of two transformer tests: opencircuit test and short-circuit test. INSULATION DRYING Construction of oil-filled transformers requires that the insulation covering the windings be thoroughly dried before the oil is introduced. There are several different methods of drying. Common for all is that they are carried out in vacuum environment. The vacuum makes it difficult to transfer energy (heat) to the insulation. For this there are several different methods. The traditional drying is done by circulating hot air 33

over the active part and cycle this with periods of hot-air vacuum (HAV) drying. More common for larger transformers is to use evaporated solvent which condenses on the colder active part. The benefit is that the entire process can be carried out at lower pressure and without influence of added oxygen. This process is commonly called vapour-phase drying (VPD). For distribution transformers, which are smaller and have a smaller insulation weight, resistance heating can be used. This is a method where current is injected in the windings to heat the insulation. The benefit is that the heating can be controlled very well and it is energy efficient. The method is called low-frequency heating (LFH) since the current is injected at a much lower frequency than the nominal of the grid, which is normally 50 or 60 Hz. A lower frequency reduces the effect of the inductance in the transformer, so the voltage needed to induce the current can be reduced. The LFH drying method is also used for service of older transformers. TERMINALS Very small transformers will have wire leads connected directly to the ends of the coils, and brought out to the base of the unit for circuit connections. Larger transformers may have heavy bolted terminals, bus bars or high-voltage insulated bushings made of polymers or porcelain. A large bushing can be a complex structure since it must provide careful control of the electric field gradient without letting the transformer leak oil. BUSHINGS

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A bushing is a hollow electrical insulator through which a conductor may . Bushings are used where high voltage lines must through a wall or other surface, on switchgear, transformers, circuit breakers and other high voltage equipment. DESCRIPTION The bushing is a hollow insulating liner that fits through a hole in a wall or metal case, allowing a conductor to along its centre and connect at both ends to other equipment. The purpose of the bushing is to keep the conductor insulated from the surface it is ing through. Bushings are often made of wet-process fired porcelain, and may be coated with a semiconducting glaze to assist in equalizing the electrical stress along the length of the bushing. The inside of the bushing may contain paper insulation and the bushing is often filled with oil to provide additional insulation. Bushings for medium-voltage and lowvoltage apparatus may be made of resins reinforced with paper. The use of polymer bushings for high voltage applications is becoming more common. The largest high-voltage bushings made are usually associated with high-voltage directcurrent converters. 35

Capacitor types Some of the higher voltage types (layers of conductive paper, film, ink or aluminum foil are used with an insulating medium) are called capacitor bushings because they form a low value capacitor between the conductor and the wall. This is done to disperse the electrical field stress and thus reduce the peak stress that could cause breakdown. BUSHING FAILURE Bushings sometimes fail due to partial discharge degradation in the insulation. There is at present great interest in the electricity supply industry in monitoring the condition of high voltage bushings. APPLICATIONS

electrical substation showing 220kV/66kV transformers, each with a capacity of 185MVA A major application of transformers is to increase voltage before transmitting electrical energy over long distances through wires. Wires have resistance and so dissipate electrical energy at a rate proportional to the square of the current through the wire. By transforming electrical power to a highvoltage (and therefore low-current) form for transmission and 36

back again afterward, transformers enable economical transmission of power over long distances. Consequently, transformers have shaped the electricity supply industry, permitting generation to be located remotely from points of demand. All but a tiny fraction of the world's electrical power has ed through a series of transformers by the time it reaches the consumer. Transformers are also used extensively in electronic products to step down the supply voltage to a level suitable for the low voltage circuits they contain. The transformer also electrically isolates the end from with the supply voltage. Signal and audio transformers are used to couple stages of amplifiers and to match devices such as microphones and record players to the input of amplifiers. Audio transformers allowed telephone circuits to carry on a two-way conversation over a single pair of wires. A balun transformer converts a signal that is referenced to ground to a signal that has balanced voltages to ground, such as between external cables and internal circuits. The principle of open-circuit (unloaded) transformer is widely used for characterisation of soft magnetic materials, for example in the internationally standardized Epstein frame method. MANUFACTURING SECTIONS INVENTORY It is the section of storage of raw material. FABRICATION 37

Fabrication is nothing but production.It is basically a machine / preparation shop. This section has following machines: 



   



 

Pacific Hydraulic Shear & pressure: Hydraulically operated machine to cut to sheet of different thickness. It contain pressure holder which is used to flatten the sheet. CNC (Computerized Numerical control) Flame cutting machine: Used to cut complicated shaft item using OXY-ACETYLENE flame. Maximum 6 torches are used in it. Cutting is done on the basis of computer programming. Rolling Machine: used for making cylindrical shape from a sheet. Bending Machine: Hydraulically operated machine used to bend the job. Hydraulic power press: Has the capacity of 100 tons used to flatten the object. Nibbling Machine: used to do various tasks like straight cutting, circle cutting, nibbling, slot cutting, circular and square punching. Hydraulic Guillotine Shear: It is to cut the sheet which has maximum cross section area of (3200*13 sq.mm). Butler machine: used for facing, tapering, & slot cutting. Plasma Cutting Machine: used for non ferrous metal.

ASSEMBLY SHOP: It is an assembly shop where different part of tank 38

comes . Hear welding processes are used for assembly, after which a rough surface is obtained and is eliminated by grinding. Grinding operates at 1200 RPM. It is assembly shop dealing with making different objects like.      

Tank Assembly Tank cover assembly End frame assembly Cross feed assembly Core Clamp assembly Pin & pad assembly

Before assembly, short blasting is done on different part of jobs to clean the surface before painting. After assembly some tests are done as non-destructive tests like. 1.

2.

3.

4. 5.

Ultrasonic Test: To detect the winding fault on CRO. At the fault place high amplitude waves are obtain. Die Penetration Test: Red solution is put at the welding and then cleaned. After some time white solution is put. Appearance of red spot indicates a fault at the welding. Magnetic crack detection: magnetic field is created and then iron powder is put on the welding. Sticking of the iron powder in the welding indicates the fault. X-Ray Test: It is same as human testing and a fault is seen in X-ray. Air / Vacuum Test: the air is filled inside the body of transformer, than soap solution is produced outside the body. If the holes appear, it is indicate the fault. 39

MACHINE SECTION: To operation to form small components of power and traction transformer are done is this section. The shop consists of following machines. 

CENTRAL LATHE: It consist one tail stock, head stock. Lower part of tail stock is fixed and tail stock spindle is moving. On this machine is facing, turning and threading is done.



TURRET LATHE: Its function is same as central lathe machine but it is used for mass production. Here turret head is used in presence of tail stock because turret head contains many tailstocks around six.



CAPSTAN LATHE: It is belt driven.



RADIAL ARM DRILLING MACHINE: Used for drilling and boring.



HORIZONTAL BORING MACHINE: It is computerized and used for making bore, facing etc.



MILLING MACHINE: a.

HORIZONTAL MILLING MACHINE: Used for making gear and cutting operations.

b.

VERTICAL MILLING MACHINE: The machine does facing, slot cutting and T-slot cutting. 40

COPPER SECTION: o o

o

o o

Tube slitting Machine: used for cutting the tube along its length and across the diameter. HYDRAULIC SHEARING MACHINE: It is hydraulically operated and its blade has V-shape and a thickness 15 mm. WATER COOLED BRAZING MACHINE: It contains two carbon brushes. The sheet is put along with sulfas sheet and the carbon brushes are heated. A lap t is formed between the sheets as the sulfas sheets melts. LINCING BELT MACHINE: It creates a smooth surface. SOLDER POT MACHINE: It has a pot that contains solder. Solder has composition of 60 % Zn and 40 % Pb.

TOOLING MACHINING: In this section the servicing of tools is done. Blade sharp machine  Mini surface grinding Machine(used for grinding purpose)  Tool and surface grinding Machine(used to grind the tool)  Drill grinding Machine (to grid the drills) 

WINDING, COIL AND MOULDS SECTION TYPES OF WINDING  Reverse section winding 41

   

Helical winding Spiral winding Interleaved winding Half section winding

The type of winding depends upon the job requirement. Also, the width and thickness of conductors designed and decided by design department. TYPES OF COIL 1. 2. 3. 4.

Low voltage coil High voltage coil Tertiary coil Tap coil

THE MOULDS ARE OF FOLLOWING TYPES 1. 2. 3.

Belly type Link type Cone type

LAMINATION AND PUNCHING SHOP The lamination used in power, dry and ESP transformer etc. for making core is cut in this section. CRGO (cold rolled grain oriented) silicon steel is used for lamination, which is imported in India from Japan, U.K and . It is available in 0.27&0.28 mm. For the purpose of cutting and punching the core three machines are installed in the shop.  Slitting machine (used to cut CRGO sheets in different width) 42

CNC cropping line pneumatic  CNC cropping line hydraulic INSULATION SHOP 

Various type of insulation are: 



    

AWWW: all wood water washed press paper. The paper is 0.2-0.5 mm thick cellulose paper is bound on conductor for insulation. Pre-Compressed Board: this is widely used for general insulation and separation of conductors in the form of blocks. Press Board: this is used for separation of coil e.g. LV from HV. It is up to 38 mm thick. Fiber Glass: this is resin material and is used in fire prone area. Bakelite Gasket: used for protection against leakage. Silicon Rubber Sheet: It is used for dry type transformer.

Insulation between windings The great majority of transformers are constructed with two or more windings which are electrically insulated from each other. In some cases a single winding is employed, parts of the winding functioning as both primary and secondary. These transformers are called autotransformers. They are frequently used when the voltage ratio is small. Autotransformers should never be used for high voltage ratios, as the low-voltage winding is not insulated from the highvoltage one, so that in case of trouble it would be dangerous to both life and equipment. 43

Machine used for shaping the insulation material are: 1. 2. 3. 4. 5. 6. 7. 8. 9.

Cylindrical machine Circular cutting machine Bending machine Punching press machine Drilling machine Guillotine machine Bench saw Jig saw Circular saw

MANUFACTURING PROCESS

44



CORE ASSEMBLY



Power Systems transformers are of the “Core Form” design. All cores are stacked, using high-quality grain-oriented silicon steel laminations, purchased slit-to-width and coated with carlite to increase the interlamination resistance and to reduce eddy current losses. Where loss evaluations justify its use, laser or mechanically scribed or plasma treated silicon steel will be used.



All cores utilize the step lap principle in the corner ts to reduce losses, magnetizing current and sound level. The cores are fully-mitered on all ts in order to improve the flux distribution.



Ultra modern computerized core shears supply fully-mitered, high-efficiency cores. These machines are able to shear the maximum width of core steel currently available.



Some machines automatically stack the legs and yokes to minimize steel handling and mechanical stresses, helping to guarantee the designed loss level.

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

The laminations are stacked in steps, resulting in a circular core shape which gives the windings optimum radial , especially during short-circuit conditions.



The exposed edges of all finished cores are bonded with low viscosity, high-strength epoxy resin on the legs and bottom yoke to help lower the sound level. The temperature rise of the core is designed to be low and is controlled, if necessary, by careful placement of vertical oil ducts within the core packets.



The core is clamped using structural steel clamps which provide high strength under both static (lifting and clamping) and dynamic (short-circuit) mechanical loads. The clamps are very lightweight for their strength and provide a smooth surface facing the winding ends, eliminating regions of high local electrical stress.

Under this process bonded core design is used to eliminate hold notching clamp and to minimize fixed losses and magnetizing current. The clamping frames for top and bottom yokes are incorporated into the still age but this must also provide rigidity for the limbs until the core has been lifted in the vertical positions for assembling of the winding.  COIL WINDINGS AND INSULATION ASSEMBLE Coil winding is of two Types: The precise details of the winding arrangements will be varied according to the rating of the transformers. The general principles remain the same throughout most the range of 46

transformer. The copper or Alluminium strips/wires used in winding are meticulously selected for its quality to give the best output. 1. L.V.Coil 2. H. V. Coil 1. L. V. COIL WINDING: The Low Voltage coil is designed to approximately match the current rating of the available low-voltage (LV). The L.V. coil is normally wound on robust tube of insulation material and this is almost invariably of synthetic resin-bonded paper. This material has high mechanical strength and is capable of withstanding the high loading. Electrically it will probably have sufficient dielectric strength to withstand the relatively modest test voltage applied to the L.V. winding during the repairing without any additional insulation. 2. H. V. COIL COIL WINDING: The second process is H.V. Coil Winding, which are wound with strip conductor and it usually consists of continuous disc type. The coils are usually created in layers and ideally all the ts are extremely well brazen and insulated in order to withstand difficult service conditions and tests.

47

The LV windings are made from Paper covered Copper Strip and placed nearest to the core. The HV winding are wound with Super Enameled Copper Wire or Aluminium wire or Paper covered Round wire or paper covered Strip depending upon the rating of the transformers. The cross section of the conductor is also chosen to keep the thermal gradient in the winding to a minimum and thus increase the life. The coils are assembled with the best insulating material avail and they are adequately clamped by the use of permawood rings where necessary to give required mechanical strength. The tappings are provided o the external HV windings. The off circuit tapping swich is gang operated type and good is maintained by means of floating spring pressure. Teh tapping swich can be looked in ay desired position. The transformer preferably off capacity 2000 KVA and above can be supplied with on load tap changer alongwith the desired controls as per the requirement. 

TESTING

The testing room is climatically controlled and is fully equipped with facilities for conducting all routine tests and temperature- rise tests. The transformers are tested at various stages of manufacture and various rating transformers are 48

tested at independent institution to establish short circuit and insulating capacity of the transformers and also the impluse withstanding withstanding capacity. Prior to shipment, all transformers manufactured BHEL are tested in accordance with the latest applicable standards according to customer specifications. All industry standard and optional tests with the exception of short-circuit tests, can be performed in-house by trained personnel using accurate and modern test equipment. 

Impulse Testing A state-of-the-art digital impulse recording system, the Haefely HIAS system, provides the most accurate analysis of impulse results available today. Electronic recording of the impulse current and voltage waveforms allows quick mathematical comparisons to be made, including the difference between the two waveforms under scrutiny. Accurate printed and plotted final results are quickly available. If required, photographic transparencies from the impulse oscilloscope can be supplied. The construction of the test area incorporates a complete copper mesh ground mat system, with extensive grounding points provided. This eliminates high impedance grounds and provides exceptionally clean test records. The impulse generator is rated at 200 kV per stage for a total of 2.8 MV, with 210 kJ total stored energy. For precise triggering, this generator is equipped with a pressurized polytrigatron gap in each stage. For chopped wave tests, a Haefely multiple chopping gap is used. Our plants are fully capable of performing lightning impulse, switching impulse and front-ofwave tests as required. 49



Induced Testing For induced testing, a variable voltage alternator, rated 1500/1000 kVA, 3/1-phase, 170/240 Hz, is used. Voltage control is by solid state automatic voltage regulator, and solid state speed control of the 1000 kW DC driving motor. During the induced test, partial discharge measurements both in pC and μV are taken and equipment is available to locate internal partial discharges by the triangulation method.



Loss Measurement Power is provided to the loss measuring system by a 5/10 MVA regulating transformer feeding three single-phase 10 MVA variable ratio transformers and a 110 MVAR capacitor bank. Losses are measured by an automated system using CTs for current and gas capacitors for voltage. This system has a fully automated digital readout and printer.



AC Testing A test supply with an output voltage infinitely adjustable from 3-350 kV is available for high voltage AC testing. To measure the applied voltage level, a digital peak-responding RMS calibrated voltmeter capable of measuring up to 1600 kV is used. WATER TURBINE A water turbine is a rotary engine that converts kinetic and potential energy of water into mechanical work. 50

Water turbines were developed in the 19th century and were widely used for industrial power prior to electrical grids. Now they are mostly used for electric power generation. Water turbines are mostly found in dams to generate electric power from water kinetic energy.

THEORY OF OPERATION Flowing water is directed on to the blades of a turbine runner, creating a force on the blades. Since the runner is spinning, the force acts through a distance (force acting through a distance is the definition of work). In this way, energy is transferred from the water flow to the turbine 51

Water turbines are divided into two groups; reaction turbines and impulse turbines. The precise shape of water turbine blades is a function of the supply pressure of water, and the type of impeller selected. Reaction turbines Reaction turbines are acted on by water, which changes pressure as it moves through the turbine and gives up its energy. They must be encased to contain the water pressure (or suction), or they must be fully submerged in the water flow. Newton's third law describes the transfer of energy for reaction turbines. Most water turbines in use are reaction turbines and are used in low (<30 m or 100 ft) and medium (30–300 m or 100–1,000 ft) head applications. In reaction turbine pressure drop occurs in both fixed and moving blades. It is largely used in dam and large power plants Impulse turbines Impulse turbines change the velocity of a water jet. The jet pushes on the turbine's curved blades which changes the direction of the flow. The resulting change in momentum (impulse) causes a force on the turbine blades. Since the turbine is spinning, the force acts through a distance (work) and the diverted water flow is left with diminished energy. An impulse turbine is one which the pressure of the fluid flowing over the rotor blades is constant and all the work output is due to the change in kinetic energy of the fluid. Prior to hitting the turbine blades, the water's pressure (potential energy) is converted to kinetic energy by a nozzle and focused on the turbine. No pressure change occurs at the 52

turbine blades, and the turbine doesn't require a housing for operation. Newton's second law describes the transfer of energy for impulse turbines. Impulse turbines are often used in very high (>300m/1000 ft) head applications. Power The power available in a stream of water is; where:     



power (J/s or watts) turbine efficiency density of water (kg/m³) acceleration of gravity (9.81 m/s²) head (m). For still water, this is the difference in height between the inlet and outlet surfaces. Moving water has an additional component added to for the kinetic energy of the flow. The total head equals the pressure head plus velocity head. = flow rate (m³/s)

STEAM TURBINE A steam turbine is a device which extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft. Its modern manifestation was invented by Sir Charles Parsons in 1884. Because the turbine generates rotary motion, it is particularly suited to be used to drive an electrical generator – about 90% of all electricity generation in the United States (1996) is by use of 53

steam turbines. The steam turbine is a form of heat engine that derives much of its improvement in thermodynamic efficiency from the use of multiple stages in the expansion of the steam, which results in a closer approach to the ideal reversible expansion process.

PRINCIPLE OF OPERATION AND DESIGN An ideal steam turbine is considered to be an isentropic process, or constant entropy process, in which the entropy of the steam entering the turbine is equal to the entropy of the steam leaving the turbine. No steam turbine is truly isentropic, however, with typical isentropic efficiencies ranging from 20– 54

90% based on the application of the turbine. The interior of a turbine comprises several sets of blades or buckets. One set of stationary blades is connected to the casing and one set of rotating blades is connected to the shaft. The sets intermesh with certain minimum clearances, with the size and configuration of sets varying to efficiently exploit the expansion of steam at each stage. OPERATION AND MAINTENANCE Because of the high pressures used in the steam circuits and the materials used, steam turbines and their casings have high thermal inertia. When warming up a steam turbine for use, the main steam stop valves (after the boiler) have a by line to allow superheated steam to slowly by the valve and proceed to heat up the lines in the system along with the steam turbine. Also, a turning gear is engaged when there is no steam to slowly rotate the turbine to ensure even heating to prevent uneven expansion. After first rotating the turbine by the turning gear, allowing time for the rotor to assume a straight plane (no bowing), then the turning gear is disengaged and steam is itted to the turbine, first to the astern blades then to the ahead blades slowly rotating the turbine at 10–15 RPM (0.17– 0.25 Hz) to slowly warm the turbine. The warm up procedure for large steam turbines may exceed ten hours. During normal operation, rotor imbalance can lead to vibration, which, because of the high rotation velocities, could lead to a blade breaking away from the rotor and through the casing. To reduce this risk, considerable efforts are spent to balance the turbine. Also, turbines are run with high quality steam: either superheated (dry) steam, or saturated steam with a high dryness fraction. This prevents the rapid impingement and erosion of the blades which occurs when condensed water is blasted onto the blades (moisture carry over). Also, liquid water entering the 55

blades may damage the thrust bearings for the turbine shaft. To prevent this, along with controls and baffles in the boilers to ensure high quality steam, condensate drains are installed in the steam piping leading to the turbine. Maintenance requirements of modern steam turbines are simple and incur low costs (typically around $0.005 per kWh); their operational life often exceeds 50 years. LARGE ELECTRICAL MACHINES The academic study of electric machines is the universal study of electric motors and electric generators. By the classic definition, electric machine is synonymous with electric motor or electric generator, all of which are electromechanical energy converters: converting electricity to mechanical power (i.e., electric motor) or mechanical power to electricity (i.e., electric generator). The movement involved in the mechanical power can be rotating or linear. Although transformers do not contain any moving parts they are also included in the family of electric machines because they utilise electromagnetic phenomena. CLASSIFICATIONS: Permanent magnet machines: PM machines have permanent magnets in the rotor which set up a magnetic field. The magnetomotive force in a PM (caused by orbiting electrons with aligned spin) is generally much higher than what is possible in a copper coil. The copper coil can, however, be filled with a ferromagnetic material, which gives the coil much lower magnetic reluctance. Still the magnetic field created by modern PMs (Neodymium magnets) 56

is stronger, which means that PM machines have a better torque/volume and torque/weight ratio than machines with rotor coils under continuous operation. This may change with introduction of superconductors in rotor. Brushed machines Brushed machines are machines where the rotor coil is supplied with current through brushes in much the same way as current is supplied to the car in an electric slot car track. More durable brushes can be made of graphite or liquid metal. It is even possible to eliminate the brushes in a "brushed machine" by using a part of rotor and stator as a transformer which transfer current without creating torque. Brushes must not be confused with a commutator. The difference is that the brushes only transfer electric current to a moving rotor while a commutator also provide switching of the current direction. Induction machines Induction machines have short circuited rotor coils where a current is set up and maintained by induction. This requires that the rotor rotates at other than synchronous speed, so that the rotor coils are subjected to a varying magnetic field created by the stator coils. An induction machine is an asynchronous machine. Induction eliminates the need for brushes which is usually a weak part in an electric machine. It also allows designs which make it very easy to manufacture the rotor. A metal cylinder will work as rotor, but to improve efficiency a "squirrel cage" rotor or a rotor with closed windings is usually used.

57

Reluctance machines Reluctance machines have no windings in rotor, only a ferromagnetic material shaped so that "electromagnets" in stator can "grab" the teeth in rotor and move it a little. The electromagnets are then turned off, while another set of electromagnets is turned on to move stator further. Another name is step motor, and it is suited for low speed and accurate position control. Reluctance machines can be supplied with PMs in stator to improve performance. The “electromagnet” is then “turned of” by sending a negative current in the coil. When the current is positive the magnet and the current cooperate to create a stronger magnetic field which will 58

improve the reluctance machine’s maximum torque without increasing the currents maximum absolute value.

TRACTION MOTOR A traction motor is an electric motor used for propulsion of a vehicle, such as an electric locomotive or electric roadway vehicle. Traction motors are used in electrically powered rail vehicles such as electric multiple units and other electric vehicles such as electric milk floats, elevators, conveyors, and trolleybuses, as well as vehicles with electrical transmission systems such as diesel-electric, electric hybrid vehicles, and battery electric vehicles.

59

Mounting of motors Usually, the traction motor is three-point suspended between the bogie frame and the driven axle; this is referred to as a "nose-suspended traction motor". The problem with such an arrangement is that a portion of the motor's weight is unsprung, increasing unwanted forces on the track. In the case of the famous Pennsylvania Railroad GG1, two bogie-mounted motors drove each axle through a quill drive. The "Bi-Polar" electric locomotives built by General Electric for the Milwaukee Road had direct drive motors. The rotating shaft of the motor was also the axle for the wheels. In the case of French TGV power cars, a motor mounted to the power car’s frame drives each axle; a "tripod" drive allows a small amount of flexibility in the drive train allowing the trucks bogies to pivot. By mounting the relatively heavy traction motor directly 60

to the power car's frame rather than to the bogie, better dynamics are obtained allowing better high-speed operation Windings The DC motor was the mainstay of electric traction drives on both electric and diesel-electric locomotives, street-cars/trams and diesel electric drilling rigs for many years. It consists of two parts, a rotating armature and fixed field windings surrounding the rotating armature mounted around a shaft. The fixed field windings consist of tightly wound coils of wire fitted inside the motor case. The armature is another set of coils wound round a central shaft and is connected to the field windings through "brushes" which are spring-loaded s pressing against an extension of the armature called the commutator. The commutator collects all the terminations of the armature coils and distributes them in a circular pattern to allow the correct sequence of current flow. When the armature and the field windings are connected in series, the whole motor is referred to as "series-wound". Power control As the DC motor starts to turn, interaction of the magnetic fields inside causes it to generate a voltage internally. This back EMF (electromotive force) opposes the applied voltage and the current that flows is governed by the difference between the two. As the motor speeds up, the internally generated voltage rises, the resultant EMF falls, less current es through the motor and the torque drops. The motor naturally stops accelerating when the drag of the train matches the torque produced by the motors. To continue accelerating the train, series resistors are switched out step by step, each step increasing the effective voltage and thus the current and torque 61

for a little bit longer until the motor catches up. This can be heard and felt in older DC trains as a series of clunks under the floor, each accompanied by a jerk of acceleration as the torque suddenly increases in response to the new surge of current. When no resistors are left in the circuit, full line voltage is applied directly to the motor. The train's speed remains constant at the point where the torque of the motor, governed by the effective voltage, equals the drag - sometimes referred to as balancing speed. Rating Electric locomotives usually have a continuous and a one-hour rating. The one-hour rating is the maximum power that the motors can continuously develop over a one hour period without overheating the motors. Such a test starts with the motors at +25 °C (and the outside air used for ventilation also at +25 °C). In the USSR per GOST 2582-72 with class N insulation, the maximum temperatures allowed for DC motors were 160 °C for the armature, 180 °C for the stator, and 105 °C for the collector.[3] The one-hour rating is typically about ten percent higher than the continuous rating, and limited by the temperature rise in the motor. In diesel-electric and gas turbine-electric locomotives, the horsepower rating of the traction motors is usually around 81% that of the prime mover. This assumes that the electrical generator converts 90% of the engine's output into electrical energy and the traction motors convert 90% of this electrical energy back into mechanical energy. Calculation: 90% × 90% = 81%. INSULATION 62

INSULATION CLASSIFICATION:Thermal classification of insulation depends upon the temperature Withstand capability of the insulation. Class – Y

up to 90 C

Class – A

up to 105 C

Class – E

up to 120 C

Class – B

up to 130 C

Class – F

up to 150 C

Class – H

up to 180 C

Class – C

180 C up to 220 C. INSULATION TESTING

Insulation:The bar is insulated with the given number of layers to build the wall thickness of insulation subjected to the generating voltage of the machine. Impregnation and baking:a) Thermo reactive system:63

In case of rich resin insulation the bar is pressed in closed box in heated condition and baked under pressure and temperature as per requirement for a given period. b) Micalastic system:In case of poor resin system the insulated bars are heated under vacuum and the impregnated (dipped) in heated resin so that all the air gaps are filled, layer by layer, with resin. Then extra resin is drained out and bars are heated and baked under pressed condition in closed box fixture. VPI Micalastic system:The bars already lay in closed fixture and full fixture is impregnated (dipped) in resin and then fixture with box is baked under given temperature for given duration. VIP Micalastic system:The individual (separate) bar is heated in vacuum and impregnated in resin. Then bar is taken out and pressed in closed box fixture and then baked at given temperature for given duration. Finishing:64

The baked and dimensionally correct bars are sanded-off to smoothen the edges and the surface is calibrated, if required, for the dimension. Conducting varnish coating:i) O (Outer Corona Protection) coating:The black semi-conducting varnish coating is applied on the bar surface on the core length. ii) E (End Corona Protection) coating:The grey semi-conducting varnish is applied at the bend outside core end of bars in gradient to prevent from discharge and minimize the end corona. Testing:a) Tan∆ test:This test is carried out to ensure the healthiness of dielectric (Insulation) i.e. dense or rare and measured the capacitance loss. b) H.V. Test:Each bar is tested momentary at high voltage increased gradually to three times higher than rated voltage. 65

66